Hi just a quick follow-up video to one I Did a couple of weeks back on why digital Illos Scopes appear in quot marks to be so noisy compared to Old analog Scopes And if you haven't seen that video, click somewhere in here and I will link it in or clck down below if you're not. Uh, following the annotations on YouTube and there were basically four main reasons why a Dig Oscilloscopes can appear more noisier than an analog scope even though they actually aren't. One was memory depth, the second one was the analog bandwidth, and the third one was uh, the lack of or when they can appear less noisy when you include things like Box Car average in or high resolution mode and fourth was the intensity graded display of available on Modern digital storage Scopes And um, the answer was is that modern digital scope Scopes are not any noisier than analog. they're just better.

They're better at showing what's really on your signal here, and how analog oscilloscopes may actually be worse in that case, in that they're hiding that highfrequency content which modern digital oscilloscope show well. I Just wanted to quickly update you on uh, two more subtle things that can also affect the apparent noise on the displayed waveform on a digital scope. Let's take a quick look at them now. I've chosen the Agilant Infin Vision Msox 3000 scope here.

Uh, because this is this appears to be in quote marks the noisiest scope that I have in my lab. and if you saw that I compared a couple of Uh Digital Storage Ill Scopes in the previous video. Well, if you've uh, seen me use this scope in videos, you might have seen a waveform like this. look I look I've got no.

Nothing connected to Channel One here. Channel 1 is set to 50 ohms input impedance, right? It's not even high impedance. Makes no difference if I terminate that input at all and look at that I'm one Vol per Division and look at the noise on that waveform. Oh, you would think that this is the world's noisiest oscilloscope, and well, as you know from the previous video, it's not.

And it's precisely because this is one of the world's best oscilloscopes. In this price performance bracket is why it is appearing to be so noisy and if we wind it down, look, uh, here we go: 50 MTS per Division 10 5 MTS per division 2 m volts per division 50 ohms input terminated. Are you kidding me? I switched that to one make you can see there's not a huge amount difference there. Are you kidding me? Look at that.

That's a whole division. Unbelievable. How bad is this oscilloscope? Well, it's not bad. it's actually brilliant.

So let's go back to one volt per division here and I'll show you why why this particular oscilloscope appears to be one of the noisiest. Scopes I.E has displays a visually thick line like this. Um, in addition to those four things that we saw in the previous video. Well, as you should know, this is one of the world's quickest.

Scopes And check out down here: I've got it connected up. uh, the trigger out from the oscilloscope. I've got it connected to my frequency counter down here and you should know that this scope has an incredible waveform update speed of 1 million or you know, roundabout. Claimed 1 million waveform updates per second.

and yes, it actually gets slightly more than that. Check it out 1.03 megahertz or you know, over a million waveform updates per second. And it's those incredibly High update speed which is showing additional noise on this waveform here compared to another oscilloscope that would have slower update rate. So how do we prove this? Well, it turns out to be very easy and let's demonstrate all we have to do is slow down the update rate of this oscilloscope and we should see the corresponding amount or the apparent amount of noise on that waveform.

Uh, reduce. So how do we do that at the moment? we're in auto trigger and then we're just triggering from Channel one so it's just Auto uh, free running trigger because we don't have any signal actually uh, hooked into it. But what we can do is we can go into the uh uh trigger mode. We go into the coupling mode.

Here we can go into if we go into normal mode. you can see that there's no trigger event at the moment so it's actually stopped. and you can get a hint of it. look at how thin that line has suddenly become.

Uh, well. what happens if we go into the trigger menu here and we set the source trigger Source Here to the internal wave gem because this has a Function Gen built in. You can do this yourself using in an external function generator into your Uh trigger into the oscilloscope or another. Channel Okay, we can go into our Wave Gen here and you'll notice that our frequency is 10 MHz Well, what happens if we lower that frequency and what I'll do is I'll show you this on the display as well and show you the value.

Drop in. So we're currently at 966 th000 waveform updates per second. 966 khz. Okay, let's adjust that frequency.

You can see the frequency here drop so it won't start dropping until we get below a megahertz or so. Here we go. Well, we're only getting you know, 870 waveform updates per second. Here we go.

So now it should drop because the frequency corresponds to there we go. The waveform update speed corresponds to our trigger frequency almost precisely. There's hardly any delay in there at all for uh, for processing that information and displaying the waveform update on the screen because the Agilant has the Meaz Zoom 4 as does it all in that as Hardware It's really, really quick, so you'll find that these two are going to match so we can adjust this to any waveform update rate we like. and you'll see the way it hasn't changed because you know 200,000 waveform updates per second.

We won't see it change much until we get down to like. You know, like tens of Hertz hundreds of Hertz something like that Okay 10 khz waveform update rate. It's still quite similar. Okay, and and let's get down there and you can see it's still matching 7.7 khz.

Let's go all the way down. Let's not muck around. Aha, Look there we go. A Kilohertz, you can start seeing the waveform.

Look, look at that and I'm not changing anything else. This is still 1 volt per Division, 10 Nan and 10 NS per division. All I'm doing is adjusting how many times a second this wave form is being captured and uh displayed effectively and we're getting Once we get down to 600 oddd look at that 440 Hertz Okay, look at that waveform it is. Let's go right down.

Let's you know, go down to something silly. 16 Hertz Look at that 16 wave form updates per second and you can see it going really, really quite slow there. And to prove that nothing has actually changed here, that line is still as thick as it was before. What we can do is we can go into the display menu over here and we can turn infinite persistence on so effectively.

That's simulating what we were doing before pretty much and you'll notice. Although now it's not the solid color we were getting before. but if we zoom into that over time, that is going to build up. So there you go.

I'm hoping you can see that because that line is now as thick as it was before with that dimmer information there. but that's basically exactly the same. And if I uh, clear the persistence, you can see that information build up there. It's not very good.

Let me go down in volts per Division and we'll really see it. And let's do that experiment again. But dramatically, at 2 molts per Division I won't go down to 1 molt cuz that's just a software thing in this Agilant 3000x. This is essentially the lowest Hardware um, volts per division set in that it actually goes.

Look, it's almost a full division we're getting. or nearly that, 1 million waveform updates per second. But let's drop that frequency right down. Here we go.

Let's not muck around 10 khz 3 and 1 12 khz 1 khz. And look at that. Look at that waveform change. If I go right down to whereabouts were we before at around about 16 Herz before.

look at that. it's totally changed. But I Turn on that. Well, it hasn't changed.

It appears as though it's less noisier, so now you can clearly see it there with the infinite persistance. Turn turned on. That waveform is just as noisy as it was before, but it's only that it appeared as a Sol solid line on the oscilloscope because it was just updating so damn fast. This scope was so good that you're being fooled into thinking that it's noisy when it's actually not.

It's nothing's changed. it's just how it displays the information. So let's go back in. Reverse Let's change our trigger Source Back to Channel One here.

Let's go to our Uh coupling, set it auto mode and look at that. Nothing else has changed. That signal hasn't changed, but it appears totally different on the screen. You've got to understand how your oscilloscope Works in this respect.

Otherwise, you think your scope can be a lot noisier and especially if you're doing comparisons between oscilloscopes. Really, if you want to do apples versus Apples comparisons on the noise floor of two digital Scopes Well, you have to make sure not only are they the same memory depth, the same analog bandwidth uh, theyve both both got the intensity graded display set to the same level, but also that they've got the same update rate and Sample rate as well. Now to show you where that sample rate can come into it. Uh, the Agilant always displays 4 gig samples per second here, so it won't drop from that unless I go down to where is it there you go 100 micros per Division If I go back to 50, we're still 40 gig samples per second.

But let's turn on, shall we? Let's go to the acquire menu and let's turn on that box car average in know high resolution mode as it's often called these days and you'll notice that it hasn't done much right up at this high speed. That's because there's not enough samples in there for it to actually work and do that box car average in function. It's too fast. But look what's happens if we lower our time base down, Look look at that.

it's going down Down Down. Look the magic of that box car averaging at your your slower sample rate. and because the sample rate isn't as high then your noise is going to be less at your lower sample rates. That's just how digital Scopes work and you've got to be aware of it.

And of course, I Haven't been using this scope to its full potential either because I've been I've had the intensity graded display set to 100% so it's working just like a you know, an old school one without intensity graded display. But of course, turn that down and look. the less frequent noise just hides into the background there as I explained in that previous video and there's the true average noise that you'll see on an analog scope. right in there.

There you go Digital Scopes They're just better than analog Scopes and that's why they appear noisy. So from those two videos I Hope you can better appreciate how digital Scopes work, how they display their signals, and why that, why they appear to be noisy when they actually aren't They're just a better tool than an analog scope. And how there are six different things No less than six different things. Apart from the actual uh, noise floor of the digital uh Channel itself and the analog to digital converter, you got memory depth, analog bandwidth uh, the Box Car average in the intensity, greater display, the update rate, and the sample rate.

It's ridiculous. You got to know how all these things work and how to use your digital scope. These are vastly powerful tools compared to their Uh analog predecessors. So really, if you don't know how to use them properly, Well, that's why there's this myth going around that they're noisier.

You just got to use it right and understand what is happening with them. So if you haven't seen the previous video, it's linked in down below. and if you want to discuss it, the Forum link is down below as well. and I hope you found that useful.

Catch you next time! Um.